The present invention relates to a permanent magnet rotor having a permanent magnet retention band unit for reliably and firmly securing of the permanent magnets to the rotor under operating conditions.
Permanent magnet motors are well known in the art. In such structures, the cylindrical rotor is formed with a magnetic core structure. A plurality of circumferentially distributed permanent magnets are secured to the periphery of the rotor to define a rotating magnetic field within the motor unit. The centrifugal forces which arise as a result of the rotation of the rotor require special design consideration in securing of the magnet to the rotor core. If any magnet becomes loose and is thrown outwardly, it will move into damaging engagement with the stator and may result in total destruction of the motor. At best, a loose module will require significant rebuilding and repair of the motor. Conventionally, means are provided for locking of the magnet within the core such as by a suitable adhesive and physical interlocking of the magnet to the core. A well known and widely used method includes a band member encircling the rotor and forming a securement of the permanent magnets to the rotor. In such structures, the band should be of a minimum thickness to maintain a minimal air gap between the rotor and the stator. Although various banding devices and systems are used, they are generally an expensive construction and must be carefully secured to the rotor assembly. The bands are permanently affixed in place and repair of the rotor is again at best expensive and difficult.